This invention relates generally to fasteners which are employed to fasten metal panels such as sheet metal. More particularly, the present invention relates to fasteners which are employed for fastening panel roofs.
Roofing systems for metal buildings frequently employ metal roofs comprising corrugated or trapezoidal metal panels which are fastened by conventional "sheet metal fasteners". A roofing composition is then applied to the panels to provide a water barrier. While conventional metal roof systems have proved to perform satisfactorily over time, it is indisputable that metal roofs do have a significant failure rate. A principal source of failure occurs when the fasteners loosen. If there is poor drainage or the seam seals fail, moisture may migrate to the vicinity of the fastener opening. The moisture may then lead to corrosion which eventually may attain a magnitude that jeopardizes the integrity of the roof system. A number of metal roof coating systems have been introduced to compensate for the failure problems of the conventional metal roof by enhancing the water barrier system of the roof. However, fastener failure remains a significant problem if there is inadequate roof securement.
In typical metal roof construction, the metal panels are secured by numerous sheet metal fasteners. The sheet metal fasteners are conventionally self-drilling threaded fasteners which in tandem with a washer are driven by torque guns into the metal supports. The fasteners are typically installed from on top of the roof panel in a routine labor intensive process. The panels will eventually tend to move or slide due to structural settling and also due to environmental factors such as wide temperature differentials, intense heat, winds, and the impact of rain and snow including their collection onto the roof structure. The sliding-type movements of the panels tend to force the fasteners sideways and eventually upwardly out of locking relationship. The immediate vicinity of the panel surrounding the fastener opening which is exposed by the loosened fastener becomes a source of collection of moisture and ultimately a source of corrosion, so that the fastener provides no securement function whatsoever. If fastener failure becomes excessive, the roof system will essentially fail and repair or replacement will be required.